Class Expression

java.lang.Object
simula.compiler.syntaxClass.SyntaxClass
simula.compiler.syntaxClass.expression.Expression
Direct Known Subclasses:
ArithmeticExpression, AssignmentOperation, BooleanExpression, ConditionalExpression, Constant, LocalObject, ObjectGenerator, ObjectRelation, QualifiedObject, RelationalOperation, RemoteVariable, TextExpression, TypeConversion, UnaryOperation, VariableExpression
public abstract class Expression extends SyntaxClass

Expression.

Simula Standard: Chapter 3 Expressions

  expression
     = value-expression
     | reference-expression
     | designational-expression
     
  value-expression
     = arithmetic-expression
     | Boolean-expression
     | character-expression
     
  reference-expression
     = object-expression
     | text-expression

Syntax used during Parsing:

Expression  =  SimpleExpression
	           |  IF  BooleanExpression  THEN  SimpleExpression  ELSE  Expression

 SimpleExpression  =  BooleanTertiary  { OR ELSE  BooleanTertiary }
 BooleanTertiary   =  Equivalence  { AND THEN  Equivalence }
 Equivalence       =  Implication  { EQV  Implication }
 Implication       =  BooleanTerm  { IMP  BooleanTerm }
 BooleanTerm       =  BooleanFactor  { OR  BooleanFactor }
 BooleanFactor     =  BooleanSecondary  { AND  BooleanSecondary }
 BooleanSecondary  =  [ NOT ]  BooleanPrimary
 BooleanPrimary    =  TextPrimary  { & TextPrimary }
 TextPrimary       =  SimpleArithmeticExpression  [ RelationOperator  SimpleArithmeticExpression ]
      RelationOperator  =  <  |  <=  |  =  |  >=  |  >  |  <> |  ==  |  =/=
 SimpleArithmeticExpression  =  [ + | - ]  Term  {  ( + | - )  Term }
 Term    =  Factor  {  ( * | / | // )  Factor }
 Factor  =  BasicExpression  { **  BasicExpression }
             
 
 BasicExpression  =  PrimaryExpression  |  {  RemoteIdentifier  |  ObjectRelation  |  QualifiedObject   }
		RemoteIdentifier =  PrimaryExpression  .  AttributeIdentifier
		ObjectRelation   =  PrimaryExpression ( IS | IN )  ClassIdentifier
		QualifiedObject  =  PrimaryExpression  QUA  ClassIdentifier

 PrimaryExpression =  ( Expression ) | Constant | ObjectGenerator | LocalObject | Variable | SubscriptedVariable
		Constant = IntegerConstant | RealConstant | CharacterConstant | TextConstant | BooleanConstant | SymbolicValue  
				BooleanConstant = TRUE | FALSE
				SymbolicValue   = NONE | NOTEXT
               ... other constants as delivered by the scanner
		ObjectGenerator  =  NEW  Identifier  "("  Expression  {  ,  Expression  }  ")"
		LocalObject = THIS ClassIdentifier
		Variable  =  Identifier
		SubscriptedVariable  =  Identifier  "("  Expression  {  ,  Expression  }  ")"

Link to GitHub: Source File.

Author:
SIMULA Standards Group, Øystein Myhre Andersen, Stein Krogdahl

  • Field Details

    • type

      public Type type
      The type

  • Constructor Details

    • Expression

      public Expression()
      Expression.

  • Method Details

    • acceptExpression

      public static Expression acceptExpression()

      Accept expression.

      Expression  =  SimpleExpression
	        |  IF  BooleanExpression  THEN  SimpleExpression  ELSE  Expression
      Returns:
      Expression or null if no expression is found.

    • expectExpression

      public static Expression expectExpression()

      Expect expression.

      Expression	=  SimpleExpression
	        |  IF  BooleanExpression  THEN  SimpleExpression  ELSE  Expression

      If no expression is found an error message is printed.

      Returns:
      Expression or null if no expression is found.

    • acceptSimpleExpression

      private static Expression acceptSimpleExpression()

      Parse simple expression.

       SimpleExpression  =  BooleanTertiary  { OR ELSE  BooleanTertiary }
 BooleanTertiary   =  Equivalence  { AND THEN  Equivalence }
 Equivalence       =  Implication  { EQV  Implication }
 Implication       =  BooleanTerm  { IMP  BooleanTerm }
 BooleanTerm       =  BooleanFactor  { OR  BooleanFactor }
 BooleanFactor     =  BooleanSecondary  { AND  BooleanSecondary }
 BooleanSecondary  =  [ NOT ]  BooleanPrimary
 BooleanPrimary    =  TextPrimary  { & TextPrimary }
 TextPrimary       =  SimpleArithmeticExpression  [ RelationOperator  SimpleArithmeticExpression ]
      RelationOperator  =  <  |  <=  |  =  |  >=  |  >  |  <> |  ==  |  =/=
 SimpleArithmeticExpression  =  [ + | - ]  Term  {  ( + | - )  Term }
 Term    =  Factor  {  (/// | / | // )  Factor }
 Factor  =  BasicExpression  { **  BasicExpression }
      Returns:
      Expression or null if no expression is found.

    • acceptANDTHEN

      private static Expression acceptANDTHEN()

      Parse Utility: Accept Boolean AND THEN.

      BooleanTertiary =  Equivalence  { AND THEN  Equivalence }
      Returns:
      an expression

    • acceptEQV

      private static Expression acceptEQV()

      Parse Utility: Accept Boolean EQV.

      Equivalence  =  Implication  { EQV  Implication }
      Returns:
      an expression

    • acceptIMP

      private static Expression acceptIMP()

      Parse Utility: Accept Boolean IMP.

      Implication =  BooleanTerm  { IMP  BooleanTerm }
      Returns:
      an expression

    • acceptOR

      private static Expression acceptOR()

      Parse Utility: Accept Boolean OR.

      BooleanTerm  =  BooleanFactor  { OR  BooleanFactor }
      Returns:
      an expression

    • acceptAND

      private static Expression acceptAND()

      Parse Utility: Accept Boolean AND.

      BooleanFactor =  BooleanSecondary  { AND  BooleanSecondary }
      Returns:
      an expression

    • acceptNOT

      private static Expression acceptNOT()

      Parse Utility: Accept Boolean NOT.

      BooleanSecondary  =  [ NOT ]  BooleanPrimary
      Returns:
      an expression

    • acceptTEXTCONC

      private static Expression acceptTEXTCONC()

      Parse Utility: Accept text concatenation.

      BooleanPrimary  =  TextPrimary  { & TextPrimary }
      Returns:
      an expression

    • acceptRelation

      private static Expression acceptRelation()

      Parse Utility: Accept relation.

      TextPrimary =  SimpleArithmeticExpression  [ RelationOperator  SimpleArithmeticExpression ]
   RelationOperator  =  <  |  <=  |  =  |  >=  |  >  |  <> |  ==  |  =/=
      Returns:
      an expression

    • acceptAdditiveOperation

      private static Expression acceptAdditiveOperation()

      Parse Utility: Accept additive operation.

      SimpleArithmeticExpression  =  UnaryTerm  {  ( + | - )  Term }
      Returns:
      an expression

    • acceptUNIMULDIV

      private static Expression acceptUNIMULDIV()

      Parse Utility: Accept unary plus and minus.

      UnaryTerm  =  [ + | - ]  Term
      Returns:
      an expression

    • acceptMULDIV

      private static Expression acceptMULDIV()

      Parse Utility: Accept multiplicative operation.

      Term  =  Factor  {  ( * | / | // )  Factor }
      Returns:
      an expression

    • acceptEXPON

      private static Expression acceptEXPON()

      Parse Utility: Accept exponentiation.

      Factor  =  BasicExpression  { **  BasicExpression }
      Returns:
      an expression

    • acceptBASICEXPR

      private static Expression acceptBASICEXPR()

      Parse basic expression.

       BasicExpression  =  PrimaryExpression  |  {  RemoteIdentifier  |  ObjectRelation  |  QualifiedObject   }
		RemoteIdentifier =  PrimaryExpression  .  AttributeIdentifier
		ObjectRelation   =  PrimaryExpression ( IS | IN )  ClassIdentifier
		QualifiedObject  =  PrimaryExpression  QUA  ClassIdentifier

 PrimaryExpression =  ( Expression ) | Constant | ObjectGenerator | LocalObject | Variable | SubscriptedVariable
		Constant = IntegerConstant | RealConstant | CharacterConstant | TextConstant | BooleanConstant | SymbolicValue  
				BooleanConstant = TRUE | FALSE
				SymbolicValue   = NONE | NOTEXT
               ... other constants as delivered by the scanner
		ObjectGenerator  =  NEW  Identifier  "("  Expression  {  ,  Expression  }  ")"
		LocalObject = THIS ClassIdentifier
		Variable  =  Identifier
		SubscriptedVariable  =  Identifier  "("  Expression  {  ,  Expression  }  ")"
      Returns:
      Expression or null if no expression is found.

    • expectVariable

      private static VariableExpression expectVariable()

      Parse Utility: Expect Variable

      Variable  =  Identifier  |  SubscriptedVariable
	SubscriptedVariable  =  Identifier  "("  Expression  {  ,  Expression  }  ")"

      NOTE: That a SubscriptedVariable may be an subscripted array or a function designator.

      Returns:
      the created Variable

    • getWriteableVariable

      public VariableExpression getWriteableVariable()

      Get a writeable variable.

      This method is redefined in Variable, RemoteVariable and TypeConversion.

      Returns:
      a writeable variable or null

    • getQualification

      private static ClassDeclaration getQualification(Expression expr)
      Returns the qualification of the given simpleObjectExpression.
      Parameters:
      expr - simpleObjectExpression
      Returns:
      the qualification of the given simpleObjectExpression

    • getQualification

      public static ClassDeclaration getQualification(String classIdentifier)
      Get qualification.
      Parameters:
      classIdentifier - a class identifier
      Returns:
      the ClassDeclaration with same identifier

    • checkCompatibility

      public static boolean checkCompatibility(Expression simpleObjectExpression, String classIdentifier)
      Check compatibility between simpleObjectExpression and a classDeclaration.
      Parameters:
      simpleObjectExpression - a simple object expression
      classIdentifier - a class identifier
      Returns:
      true if compatible, otherwise false

    • evaluate

      public Expression evaluate()
      Try to Compile-time Evaluate this expression
      Returns:
      the resulting evaluated expression

    • maybeStatement

      public abstract boolean maybeStatement()
      Returns true if this expression may be used as a statement.
      Returns:
      true if this expression may be used as a statement

    • get

      protected String get()
      Generate code for getting the value of this Expression
      Returns:
      the resulting Java code

    • put

      String put(String rhs)
      Generate code for putting the value into this Expression
      Parameters:
      rhs - a evaluated expression.
      Returns:
      the resulting Java code

    • getNumber

      public Number getNumber()
      Try to evaluate this expression to a number.
      Returns:
      the resulting number or null

    • getInt

      public int getInt()
      Try to evaluate this expression to an integer.
      Returns:
      the resulting int or 0

    • buildEvaluation

      public abstract void buildEvaluation(Expression rightPart, CodeBuilder codeBuilder)
      ClassFile coding utility: Build Evaluation Code.
      Parameters:
      rightPart - expression
      codeBuilder - the codeBuilder used.

    • printTree

      public void printTree(int indent, Object head)
      Description copied from class: SyntaxClass
      Utility print syntax tree method.
      Overrides:
      printTree in class SyntaxClass
      Parameters:
      indent - number of spaces leading the lines
      head - the head of the tree.

    • toString

      public String toString()
      Overrides:
      toString in class Object